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## Class 4 - Equilibrium and Reversible Processes

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**Class 4 - Equilibrium and Reversible Processes**• Part 1 - Contact Before Work 5 min • Part 2 - Review and Report Out 45 min • Break 10 min • Part 3 - Review (continued)15 min • Part 4 - Forces & Energy Transfer10 min • Part 5 - The Equations10 min • Part 4 - Solving the Equations 10 min • Part 5 - Clarification 5 min**Begin With the End in Mind :Class Learning Objectives**• Demonstrate Knowledge LoL for • equilibrium(mechanical, thermal, electrical), • an internally reversible process, • a reversible process. • what causes a process to be irreversible, • the concept of ‘immediatesurroundings’, • the concept of ‘steadystate’, and • the ‘heattransfer’ heuristic. • Demonstrate Knowledge LoL for constructing the entropyaccounting equation.**Class 4 - Review (60 min)**Each sub-team of two persons, use a blank sheet of paper or a page from your Academic Journal to: • State the two conditions required for a system to be in equilibrium. • Name three'thermodynamicproperties of matter' that are included in the conservation and accounting equations (p. 484 and 517). • What is the relationship between equilibrium and the 'thermodynamicproperties of matter’ ? • Define an 'internally reversible', or 'quasi-equilibrium' path or process.**Class 4 - Review (cont.)**• State the entropy accounting equation for the system and identify each term as 'flow in/out', 'thermal energy transfer', 'generation' or 'accumulation'. What is our heuristic for the entropygenerationterms for the system ? • How is an internally reversible processdescribed or represented in the entropy accounting equation? (p. 518) • What are the 5essentialfeatures of a reversible process or path? (p. 519) • List the 9 major causes or sources of irreversibility in a process or path; include an example for each cause. (see p. 519)?**Class 4 - Review (cont.)**• List 6processes or paths. (see p. 518) 10 What additional constraints are required to define a reversiblepath; i.e., both internally and externally reversible? (p. 519) 11Define the term 'immediatesurroundings'; what is included and what is excluded? (p. 520) 12 Define the concept of 'steady state'. 13 State the 'heat transfer heuristic' (p. 526)**Break**Be back with your team, ready to work, in 10minutes : rememberourECE 340 Class Code of Cooperation !**Body # B,**the crank (partially hidden) Body # C, connecting rod tload Outlet C IB MC A Valve Closed MOTION Body # A, the flywheel ‘part of the load’ Valve Closed System = ‘Control Volume’ which contains the gas being compressed. Rotation Inlet Reciprocating Compressor**Structure for ‘Doing the Work’**• Specify an appropriate coordinatesystem. • Include the gravitationalfield in the surroundings; show all of the body and surface forces that the surroundings exerts on the system. • Show all of the surface forces that the system exerts on the surroundings. • Show how mass, totalenergy, and entropy are exchanged between the system and the surroundings. • Construct the totalmass conservation equation; identify each term as ‘Accumulated’ or ‘Flow In/Out’**Structure for ‘Doing the Work’**• Assume that the compressionprocess is internally reversible; what changes should be made to the labeled sketch? • Construct the total energy conservation equation; identify each term as • ‘Accumulated’ , ‘Flow In/Out’ , • ‘External Forces’ , ‘Pv’ Work , or ‘Heat’ • Construct the entropy accounting equation; identify each term as ‘Accumulated’ , ‘Flow In/Out’ , ‘Heat Transfer’, or ‘Generation’. • Multiply both sides of these equations by dt and integrate the resulting terms.**Model Analysis**1. Model Variables From the Sketch … From Equation 1 ... From Equation 2, etc. …. 2. Analysis Variables - Equations _______ Remaining Unknowns - Data - Specifications - Parameters - Initial Conditions - Independent Variables _______ Design Variables; Solvable ?**Structure for ‘Doing the Work’**• Display the essentialfeatures of the problem in a (xx min)labeled sketch. Include an appropriate coordinatesystem. • Identify an appropriate system ( or systems ). ( x min) • What extensiveproperties are to be accounted for ( x min)or conserved? • What is an appropriate timeperiod for this problem? ( x min) • State the applicable balances for the extensive properties (xx min)in tabularform. • Delineate the specifications, data, and definingrelationships. (xx min) • Analyze the model ( i.e., count variables, equations, etc. (xx min)to determine if the problem can be solved ) • Make appropriate assumptions and quantify the behavior.( ? min)